Ecoregion: Grasslands
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Grasslands
INTRODUCTION
About 25% of Earth’s land surface is covered by temperate grassland. These large expanses
of flat or hilly country cover much of North America, as well as large areas of Europe, Asia,
and South America. Most grasslands are found in the interiors of continents, where there is
too little rainfall for a forest but too much rain for a desert.
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Rolling hills covered with grasses and
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A few scattered trees are found on
Ecoregion: Grasslands
very few trees are typical of North
American grassland prairies.
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savannas, tropical grasslands of Africa.
Temperate grasslands have subtle differences and different names throughout the world.
Prairies and plains of North America are grasslands with tall grasses, while the steppes of
Russia are grasslands with short grasses. Veldts are found in South Africa, the puszta in
Hungary, and the pampas in Argentina and Uruguay.
Savannas are tropical grasslands that support scattered trees and shrubs. They often form a
transitional biome between deserts and rain forests. Some temperate grasslands are also
called savannas. The word savanna comes from the Spanish word zavanna, meaning
“treeless plain.” Savannas cover almost half of Africa (mostly central Africa) and large areas of
Australia and South America.
ABIOTIC DATA
The grassland climate is rather dry, averaging about 20 to 100 centimeters (8–40 inches) of
precipitation a year. Summers are very hot and may reach 45°C (113°F). Winter temperatures
often fall below freezing, which is 0°C (32°F). The soil of the savanna is poor in nutrients,
compared to other types of grassland.
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Data from Missouri Botanical Garden
The average rainfall for a grassland is about 75 centimeters
(30 inches) per year.
Savannas often have a season of heavy rainfall followed by a season of drought. Annual
rainfall on most savannas ranges from 76 to 100 centimeters (30–40 inches). These moist
grasslands support trees and tall grasses that may reach 3 meters (10 feet) tall. The heavy
rain sometimes washes away the top layer of soil in the savanna. Valuable nutrients that
support plant life are washed away with it. Other savanna environments receive as little as 25
centimeters (10 inches) of rain each year. Here grasses grow in short clumps, and trees are
sparse.
BIOTIC DATA
Most savanna grasses grow in clumps and have deep roots. They turn brown and stop
growing during the dry season. Trees shed their leaves to conserve moisture and energy.
Ecoregion: Grasslands
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Pronghorn antelope are found grazing
grasslands across western North
America.
Prairie dogs build extensive networks of
tunnels underground.
The animals of the temperate grassland have developed ways to survive harsh conditions.
The ground squirrel and kangaroo rat do not sweat. This helps them conserve water in the dry
season. Bison grow thick coats that protect them during the harsh winters. Some grassland
animals, such as gophers and prairie dogs, build underground burrows. They store food in
their burrows and hibernate through the winter.
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American bison once roamed the plain
in herds estimated as large as 50
million. By 1889 less than 1000 were
bison left. They were important to the
Courtesy of R. Town, U.S. Fish and Wildlife Service
The sharp-tailed grouse is a grounddwelling bird of northern brushlands and
prairies. During courtship, males gather in
open areas, inflate reddish purple air sacs
Ecoregion: Grasslands
plains Indians for food, shelter, and
clothing.
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at the sides of the neck, and emit booming
calls while strutting with tails raised and
fanned and wings fluttering and quivering.
Other animals that live or have lived in the temperate grasslands include wild horses, wolves,
prairie dogs, jack rabbits, deer, mice, coyotes, foxes, skunks, badgers, blackbirds, grouse,
meadowlarks, quail, sparrows, hawks, owls, snakes, grasshoppers, leafhoppers, and spiders.
Courtesy of John and Karen Hollingsworth, U.S.
Fish and Wildlife Sservice
There are several species of rhinoceros:
black, white, Javan, Indian, and Sumatran.
All are listed as endangered by the
International Union for the Conservation of
Nature and Natureal Resources. Once
numerous in eastern and southern Africa,
they are now found only in national parks
and game reserves.
Courtesy of Ken Stansell, U.S. Fish and Wildlife
Service
Giraffes are found in the African savanna
south of the Sahara Desert. Giraffes feed
almost exclusively on the leaves of acacia,
mimosa, and wild apricot trees. They drink
only rarely, taking in approximately 8 liters
(2 gallons) of water in a week, and can go a
long time with no water at all.
The savanna of eastern Africa has more animals than any other grassland biome. A wide
variety of animal life is adapted to the environmental conditions of this biome. For example,
large herds of antelopes, zebras, and wildebeests migrate great distances to find grass and
water. Predators, such as lions, hyenas, and cheetahs, follow and prey upon these herds.
Ecoregion: Grasslands
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ISSUES
Few natural grassland regions remain, because most have been turned into farms or grazing
land. They suit these purposes because they are flat, are covered with grass, and have rich
soil. In North America, the prairies were once inhabited by huge herds of bison and pronghorn
antelope. These animals were hunted by wolves, bears, and other predators. Where prairies
were turned into farmland, the large herds and the predators are now gone.
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The rich soils make ideal farmland.
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Overuse of the land can deplete the soil
of vital nutrients.
Overgrazing, plowing, and excess salts left behind by irrigation waters have harmed some
grasslands. Strong winds blow loose soil from the ground after plowing, especially during
Ecoregion: Grasslands
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droughts. This caused the dust storms of the Great Plains of the United States, such as
occurred during the Dust Bowl years in the 20th century.
Courtesy of John and Karen
Hollingsworth, U.S. Fish and
Wildlife Service
A service botanist looks
after an endangered
western prairie fringed
orchid in Nebraska.
Fringed orchids are found
in tallgrass prairies, most
often in moist habitats or
sedge meadows, and
require direct sunlight for
growth. They persist in
areas disturbed by light
grazing, burning, or
mowing.
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As improved agricultural methods are
found, more and more of the prairie is
converted to farmland. This circle
irrigation system conserves water and
promotes crop rotation. This circle is
approximately 0.4 kilometers (0.25
miles) in diameter.
Many species of grasses, flowers, shrubs, and bushes form the base of the food web for birds,
rodents, insects, and grazing animals. Plants and the animals that depend on them are lost
when grassland prairie is converted to other land uses.
Climate change is another issue for grasslands. Scientists continue to try to determine
whether the climate is actually warming. Although these areas receive too little rainfall to
sustain a forest, some of these areas had much denser foliage in the recent past.
Ecoregion: Grasslands
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Studies suggest that even less water may be available in the future. This would affect the use
of this land for grazing animals. If a drier climate causes some areas of the southeast or
midwest to lose their ability to sustain a forest, those areas may come to resemble grasslands.
A wetter climate, however, might enable forests to grow in areas that are now grasslands,
while also allowing grasses to grow in areas that are deserts today.